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Re: IBC 2006 - SEISMIC DESIGN OF STEEL - 2205.2.2

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Thanks, Harold.

Problem: virtually all our connections involve gussets. What then?

William L. Polhemus, Jr. P.E.
Via iPhone 3G

On Feb 21, 2009, at 1:25 AM, Harold Sprague <spraguehope(--nospam--at)> wrote:

Your colleague is correct.  ICC has a presence in the development of ASCE 7 and the intent is for the ASCE 7 to be applicable as invoked by the IBC.  The nonbuilding structures section was specifically developed in order to address the specific needs of nonbuilding (industrial structures). 
There are many industrial structures that require bracing to elements with no gusset plates at all thus the special detailing requirements are not possible.  The use of these structures could not be precluded just because they were in a region of high seismic demand.    The concept of dropping the R value to a point approximating an elastic response was specifically developed to avoid seismic detailing where seismic detailing was not feasible. 
You owe your colleague and me a beer. 

Regards, Harold Sprague

> Date: Fri, 20 Feb 2009 21:14:40 -0600
> From: bill(--nospam--at)
> To: seaint(--nospam--at)
> Subject: IBC 2006 - SEISMIC DESIGN OF STEEL - 2205.2.2
> I'm having a disagreement with a colleague regarding what I perceive to
> be a conflict between IBC 2006 Section 2205.2.2, which states that
> seismic detailing of structural steel is required in SDC D, E and F, and
> ASCE 7-05.
> Since we're doing mostly industrial, petrochemical and refinery work, we
> frequently make reference to Chapter 15 of ASCE 7. In Table 15.4-1 of
> ASCE 7, it allows the use of R = 1.5 for ordinary concentrically-braced
> steel frames in SDC "D" when you don't want to use the Seismic
> Provisions of AISC 341-05. This fellow has taken to doing this in all
> cases so that they don't have to worry about all the detailing
> provisions - in essence, they can just do a "normal" frame for
> equipments supports, platforms, etc. You end up with potentially heavier
> foundations - eh, it's just concrete - and maybe a bit more steel, but
> you don't have to worry about all the detailing for ductile behavior,
> goes that theory.
> I, however, believe that Section 2205.2.2 of IBC 2006 takes precedence,
> and overrules ASCE 7 on this score. Of course, you can still use R = 1.5
> if you want to, but you're still going to have to do the detailing.
> My friend claims I'm "reading it wrong," and seems to feel that the IBC
> 2006 applies ONLY to Chapter 12, and that Chapter 15 is another kettle
> of fish, so to speak. I respond that Chapter 15 specifically says that
> it's provisions are to be used IN ADDITION to those of Chapter 12, to
> handle non-building structures.
> And so back and forth it goes, with no resolution in sight. I think this
> guy is very "ASCE 7" oriented, whereas I'm more inclined to look at the
> hierarchy of the documents - IBC 2006 incorporates ASCE 7-05, not the
> other way around.
> Comments?
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